Complete ICS20 Implementation

.changelog/unreleased/improvements/ibc/1759-complete-ics20.md

@@ -0,0 +1 @@
+- Complete ICS20 implementation ([#1759](https://github.com/informalsystems/ibc-rs/issues/1759))

modules/Cargo.toml

@@ -43,6 +43,7 @@ sha2 = { version = "0.10.2", default-features = false }
 flex-error = { version = "0.4.4", default-features = false }
 num-traits = { version = "0.2.15", default-features = false }
 derive_more = { version = "0.99.17", default-features = false, features = ["from", "display"] }
+uint = { version = "0.9", default-features = false }
 
 [dependencies.tendermint]
 version = "=0.23.7"

modules/src/applications/mod.rs

@@ -1,3 +1,3 @@
 //! Various packet encoding semantics which underpin the various types of transactions.
 
-pub mod ics20_fungible_token_transfer;
+pub mod transfer;

modules/src/applications/transfer/acknowledgement.rs

@@ -0,0 +1,61 @@
+use super::error::Error;
+use crate::core::ics26_routing::context::Acknowledgement as AckTrait;
+use crate::prelude::*;
+use core::fmt::{Display, Formatter};
+
+use serde::{Deserialize, Deserializer};
+
+/// A string constant included in error acknowledgements.
+/// NOTE: Changing this const is state machine breaking as acknowledgements are written into state
+pub const ACK_ERR_STR: &str = "error handling packet on destination chain: see events for details";
+pub const ACK_SUCCESS_B64: &[u8] = b"AQ==";
+
+#[derive(Clone, Debug)]
+pub enum Acknowledgement {
+    /// Equivalent to b"AQ==" (i.e. `base64::encode(0x01)`)
+    Success(Vec<u8>),
+    /// Error Acknowledgement
+    Error(String),
+}
+
+impl Acknowledgement {
+    pub fn success() -> Self {
+        Self::Success(ACK_SUCCESS_B64.to_vec())
+    }
+
+    pub fn from_error(err: Error) -> Self {
+        Self::Error(format!("{}: {}", ACK_ERR_STR, err))
+    }
+}
+
+impl AsRef<[u8]> for Acknowledgement {
+    fn as_ref(&self) -> &[u8] {
+        match self {
+            Acknowledgement::Success(b) => b.as_slice(),
+            Acknowledgement::Error(s) => s.as_bytes(),
+        }
+    }
+}
+
+impl<'de> Deserialize<'de> for Acknowledgement {
+    fn deserialize<D: Deserializer<'de>>(deserializer: D) -> Result<Self, D::Error> {
+        let s = String::deserialize(deserializer)?;
+        let ack = if s.as_bytes() == ACK_SUCCESS_B64 {
+            Self::Success(ACK_SUCCESS_B64.to_vec())
+        } else {
+            Self::Error(s)
+        };
+        Ok(ack)
+    }
+}
+
+impl Display for Acknowledgement {
+    fn fmt(&self, f: &mut Formatter<'_>) -> core::fmt::Result {
+        match self {
+            Acknowledgement::Success(_) => write!(f, "AQ=="),
+            Acknowledgement::Error(err_str) => write!(f, "{}", err_str),
+        }
+    }
+}
+
+impl AckTrait for Acknowledgement {}